1. Field of the Invention
The present invention is to provide a capsule anti-sticking agent which can provide excellent anti-sticking effect on soft capsules without impairing various properties such as water activity, disintegration property and safety, a coated soft capsule of high quality which is coated with the capsule anti-sticking agent and excels in anti-sticking effect and an efficient method for manufacturing the coated soft capsule.
2. Description of the Related Art
Soft capsules have been used in a wide range of fields such as medicaments, cosmetics, foods and health foods because they are formed by membrane materials containing gelatin as main ingredient and can conveniently encapsulate oily liquids, granule, powder, tablets and the like.
However, conventional soft capsules get moistened and softened because of their hygroscopic property when stored in high temperature and high humidity environment like in summer or rainy season (at a temperature of 40° C. and a relative humidity of 75% or more, for example). As a result, adhesive property of surface of the soft capsules may be increased and sliding property of the soft capsules may be decreased, making packing and filling operations difficult, or the soft capsules may stick to each other or to the inner surface of the storage containers, and taking out of required amount of soft capsules may become difficult or the capsule membrane may be destroyed at the time of ingestion.
Therefore, various methods have been proposed in order to prevent sticking between soft capsules or between the soft capsules and the inner surface of the storage containers. For example, a method for coating surfaces of the soft capsules with anti-sticking agents (coating agents), a method for mixing anti-sticking ingredients in the membrane material of the soft capsules, and the like are known.
In the method for coating surfaces of the soft capsules with anti-sticking agents (coating agents), hydroxypropylmethylcellulose, and shellac, ethylcellulose and alkylene glycol as necessary (Japanese Patent Application Publication (JP-B) No. 49-11047), carnauba wax (Japanese Patent Application Laid-Open (JP-A) No. 56-156212), hardened oil such as castor oil, rapeseed oil, cotton-seed oil and soybean oil (JP-A No. 64-42419), hardened vegetable oil or sucrose esters of fatty acid (JP-A No. 64-79110), glyceryl fatty acid diacetate (JP-A No. 4-288011) and mixtures of film-forming materials such as cellulose derivatives and inorganic materials or organic acid metal salt (JP-A No. 8-34727) have been proposed as the anti-sticking agents, for example. However, when the soft capsules coated with these anti-sticking agents are stored in high temperature and high humidity conditions, the surface adhesive property is increased with time and anti-sticking effect becomes insufficient.
On the other hand, in the method for mixing anti-sticking ingredients in the membrane material of the soft capsules, the anti-sticking ingredients and the capsule contents may interact with each other, resulting in lack of versatility. Moreover, it is necessary to mix the anti-sticking ingredients with the membrane materials of the soft capsules in large amount in order to increase the anti-sticking effect and as a result, problems such as extended time for disintegration, defective appearance, formability degradation of the soft capsules, and the like during manufacturing arise (JP-A Nos. 2-22221, 3-98638, 5-4914, 8-169817, 10-310519 and 2000-44465).
For example, lecithin is proposed as the anti-sticking ingredient (JP-A No. 2000-336028), however, the anti-sticking effect provided by mixing in the lecithin is not satisfactory.
Meanwhile, lecithin which is mixed in the membrane ingredients of capsules for the purpose other than anti-sticking have been proposed. For example, an enzyme-digested lecithin as a carrier for bioactive compound (JP-A No. 2002-532389), a lecithin as an emulsifier (JP-A No. 2001-161306), a soybean lecithin as a plasticizer (JP-A No. 11-19503), an enzymatically decomposed lecithin as a flavoring ingredient (JP-A No. 2002-154949) have been proposed. However, the fact that the lecithin and the enzymatically decomposed lecithin that are mixed excel in anti-sticking effect of the soft capsules is not disclosed in these proposals.
Therefore, development of anti-sticking agent, which can provide excellent anti-sticking effect on the soft capsules without impairing various properties such as water activity, disintegration property and safety even when the soft capsules are stored in high temperature and high humidity environment, is desired.